The U.S. Navy has been investigating the lithium-inorganic electrolyte battery for many ocean oriented applications, such as oceanographic instrumentation, sonar systems, biotelemetry devices, undersea weapons and small undersea vehicles. The lithium-inorganic electrolyte battery is desirable because of its high-energy density and long shelf life capabilities. The lithium-inorganic electrolyte battery can be obtained from several companies including GTE Laboratories, P. R. Mallory and Company, Inc., Honeywell, Inc., and Electrochimica Corporation. The electrolyte is composed of inorganic salts (lithium aluminun chloride) in an organic solvent (thionyl chloride). Energy is produced by the electro-chemical decomposition of the inorganic solvent material at a carbon electrode and oxidation of the lithium during discharge of the cell. The cathode is constructed of a high porosity carbon which allows circulation of the catholyte and space for accumulation of reaction products. The inorganic solvent decomposes only when the load circuit is closed, thereby making it possible for the battery to operate effectively for several years.
While the aforementioned lithium battery has a high energy density it has a relatively low current flow rate at atmospheric pressure. However, when ambient pressure is increased, the battery will, for reasons not entirely known, increase its current flow rate correspondingly. A possible explanation for this increased capability with increased pressure is that the electrolyte solution more thoroughly saturates the porous carbon cathode, thereby increasing the effective surface area between the electrolyte and the carbon. This, in turn, would increase the electron exchange between the electrolyte and the carbon cathode resulting in an increase in current flow. Since many of the batteries utilized by the Navy are involved in submerged applications, it would be beneficial to utilize the depth pressure of the water to pressurize the battery and increase the current flow rate. One approach of accomplishing this result is to dispose the lithium battery within a pressure compensated housing which has a liquid interfacing with the electrolyte in the lithium battery through an aperture in the battery casing. Such an approach will result in increased current flow rate of the lithium battery with corresponding increased depth in the water. However, such an approach per se does not overcome the problem of disposition of gases generated by the lithium battery during use. These gases, in particular sulphur dioxide, is very corrosive and, upon contact with the interior surface of the housing and its associated terminals, will result in a short life battery apparatus due to the failure of the components. Accordingly, an approach is needed where the advantages of the pressure compensated apparatus can be obtained, and yet the corrosion of components can be eliminated as the battery generates gases.